A typical operating system includes a file system. The file system provides a mechanism for the storage and retrieval of files and a hierarchical directory structure for the naming of multiple files. More specifically, the file system stores information provided by the user (i.e., data) and information describing the characteristics of the data (i.e., metadata). The file system also provides extensive programming interfaces to enable the creation and deletion of files, reading and writing of files, performing seeks within a file, creating and deleting directories, managing directory contents, etc. In addition, the file system also provides management interfaces to create and delete file systems. File systems are typically controlled and restricted by operating system parameters. For example, most operating systems limit the maximum number of file names that can be handled within their file system. Some operating systems also limit the size of files that can be managed under a file system.
To access a file, the operating system (via the file system) typically provides file manipulation interfaces to open, close, read, and write the data within each file. An application, which may reside on the local system (i.e., computer) or may be located on a remote system, uses files as an abstraction to address data. Conventionally, this data is stored on a storage device, such as a disk. The file system stores data on the storage device by managing the allocation of space within the storage device.
Typically, the volume manager provides space, which is managed by the file system. Two common types of file system space allocation strategies are known as block-based allocation and extent-based allocation. Block-based allocation creates incremental disk space for each file each time the file is extended (i.e., modified via a write request to add information), whereas extent-based allocation creates a large series of contiguous blocks (i.e., extents) each time the file exhausts the space available in the file's last extent.
When allocating space, both block-based and extent-based allocation use space provided by the volume manager. The volume manager allows multiple physical disks to be used as a single volume (i.e., a virtual disk) to provide larger consolidated storage sizes and simpler management. The volume manager allows users to organize data along volume boundaries (i.e., each volume has physical disk space allocated to the volume such that the volume is tied only to that dedicated physical disk). The volume manager is typically implemented as a separate layer between the physical disks and the file system, and is presented to the user as a virtual disk device. In other words, volume managers organize the collections of physical devices (e.g., disks) into virtual devices. Additionally, the space allocated within the volume manager is handled by the file system. Consequently, the volume manager is not aware of which blocks within the available storage space are in use and which blocks are free for data to be stored.
Further, file systems may be mounted on the virtual disk devices. Thus, physical disks are partitioned and allocated to multiple virtual disk devices, and each virtual disk device is capable of having a file system that exclusively uses that particular virtual disk device. A request to access a file is typically performed by an application, via the file system, using a file name and logical offset. This file name and logical offset (i.e., the manner in which applications express file operation requests) corresponds to a location within the virtual disk device. Subsequently, the request is translated to physical disk space on the storage device by the volume manager, allowing the user of the application to access the data within a particular file.
Typically, file systems store data on disk using one of two schemes: big endian or little endian. In a file system implementing the big endian scheme, data is stored on disk such that the most significant byte (MSB) of the data is stored in memory at the lowest address, and the least significant byte (LSB) is stored at the highest address. In contrast, a file system implementing a little endian scheme, the LSB of the data is stored in memory at the lowest address, and the MSB is stored at the highest address.
Conventionally, in order to use data stored on disk using one type of scheme (i.e., big endian or little endian) on a file system that uses a different type of scheme, one of the systems must byte swap all the data that is to be used by the target system. For example, in a networking environment where multiple machines (i.e., computers, servers, etc.) are connected to the same network, there may be some machines that use a big endian scheme, and some machines that use a little endian scheme to store data. Because the networking environment (i.e., sending network traffic via Internet Protocol) as a whole functions using network byte order (i.e., a big endian scheme), all the machines that use little endian must byte swap network traffic (i.e., packets) before sending and receiving traffic to or from the network.
Existing file systems store data on physical disks using one of the two endian schemes, typically the scheme used by the CPU of the system. File systems typically use the same method described above, i.e., byte swapping, in order to migrate data to and from file systems using different underlying schemes.